Bushing (electrical)

Hollow electrical insulator Assortment of small ceramic bushings for voltages from a few hundred to a few thousand volts High-voltage bushings on a utility transformer at an electrical substation. These probably operate at several hundred thousand volts. In electric power, a bushing is a hollow electrical insulator that allows an electrical conductor to pass safely through a conducting barrier, such as the case of a transformer or circuit breaker, without making electrical contact with it. Bushings are typically made from porcelain, though other insulating materials are also used. Principle All materials carrying an electric charge generate an electric field. When an energized conductor is near a material at earth potential, it can form very high field strengths, especially where the field lines are forced to curve sharply around the earthed material. The bushing controls the shape and strength of the field and reduces the electrical stresses in the insulating material. Bushing condenser A bushing must be designed to withstand the electrical field strength produced in the insulation, when any earthed material is present. As the strength of the electrical field increases, leakage pa